EP4019177A1 - Method and device for assessing the quality of a processing process - Google Patents

Abstract

The invention relates to a method and a device (1) for assessing the quality of a machining process in which a workpiece (W) is machined with specific machining parameters (P_i(x)) along a machining path (X), wherein the machining result (R(x)) of the machining process along the machining path (X) is measured with at least one sensor (2) and at least one sensor signal (S_j(x)) is recorded and from at least one sensor signal ( S_j(x)) at least one quality parameter (Q_k(x)) is determined and the at least one quality parameter (Q_k(x) ) to assess the quality of the machining result (R(x)) of the machining process with specified quality parameter limit values (Q_k,o(x), Q_k,u(x) ) is compared. According to the invention, when assessing the quality of the machining result (R(x)) of the machining process, deviations of the machining parameters (ΔP_i(x)) from the desired values of the machining parameters (P<sub>i,soll</ sub>(x)) during the machining of the machining path (X) of the workpiece (W) along the machining path (X) automatically taken into account by the quality parameter limit values (Q'_k,o(x), Q'_k,u(x)) to the deviations of the machining parameters (ΔP_i(x)).

Description

The invention relates to a method for assessing the quality of a machining process in which a workpiece is machined with specific machining parameters along a machining path, the machining result of the machining process being measured along the machining path with at least one sensor and at least one sensor signal being recorded and at least one quality parameter being determined from at least one sensor signal is determined and the at least one quality parameter for assessing the quality of the machining result of the machining process along the machining path is compared with predefined quality parameter limit values.

Furthermore, the invention relates to a device for assessing the quality of a machining process of a workpiece with specific machining parameters along a machining path.

Machining processes include, in particular, joining processes, such as welding or soldering processes, in which workpieces are joined together or workpieces are coated, but also surface treatment processes, such as plasma machining processes, in which workpieces are treated with plasma in order to prepare them for subsequent processing. For example, the surface of workpieces can be treated with plasma before painting in order to remove residues from the surface and/or to improve the adhesion of the paint layer.

It is well known that the quality of a machining process can be monitored or assessed in order to be able to reject defective workpieces or to adjust machining parameters accordingly to improve quality. For this purpose, machining paths are examined after the machining process and the quality of the machining process is assessed from this. In the simplest case, the quality assessment can be carried out in the form of a visual assessment by expert personnel. However, the machining result of the machining process along the machining path is usually measured automatically with appropriate sensors and at least one quality parameter is determined from the sensor signals. To assess the Quality, the at least one quality parameter is compared with predefined quality parameter limit values. For example, a weld seam can be measured as a processing path of a welding process after the welding process with a camera, preferably with lighting, and the seam width and seam elevation of the weld seam can be determined therefrom with appropriate image processing algorithms and a quality parameter can be derived therefrom. Depending on the processing task or welding task, different quality parameters can be used to define the quality of the weld seam. For example, with a visible weld seam, in addition to the mechanical properties of the weld seam, it can also be important that the weld seam is as narrow and regular as possible, whereas with a weld seam that is not visible, the strength of the connection and thus a sufficient penetration depth can be more important. The at least one quality parameter that is suitable for the respective machining process is defined accordingly and then compared with specific quality parameter limit values, for example an upper and lower limit value, in order to be able to automatically assess the quality. The quality parameters are usually determined by evaluating optimally machined workpieces with IO ("okay") machining paths. In welding processes, for example, the size of the undercut, the so-called a dimension, the seam elevation, the end crater at the end of the weld seam, etc. can be used as quality parameters.

the EP 3 566 806 A1 describes a welding process as a machining process in which optimal welding parameters, which were determined using test welds on test workpieces, are used automatically for the achievement of certain quality criteria for the welding process. The optimum welding parameters for the respective welding task are determined via the optimum of a calculated quality functional using the respective optimum welding parameters of the test welds.

the EP 1 642 366 B1 and the WO 00/35622 A1 describe methods for monitoring the quality of welding processes, whereby information about the weld seam produced is compared with specified values and, in the event of deviations, the welding parameters are adjusted accordingly be adjusted or a warning is issued in the event of excessive deviations. Here, the processing parameters are regulated to specified target values.

In known quality assessment systems for machining processes, in particular welding processes, it is checked whether specific criteria lie within specified limits. For example, a weld seam that has been produced is compared with a previously defined "ideal weld seam" and the quality of the weld seam produced is assessed therefrom. However, if processing parameters are deliberately changed manually or automatically during the processing, the quality criteria are not automatically adjusted during the quality assessment, but must be carried out manually in a laborious process. This can lead to the quality of the machining process being assessed as inadequate because the changes made to the machining parameters deliberately during the machining process were not automatically taken into account. The quality of the machining process can also be assessed positively, although the result does not meet the quality criteria. For example, in a welding process it may be necessary to adjust certain welding parameters due to workpiece tolerances. For example, a larger gap width occurring due to tolerances in the workpieces or clamping devices can make it necessary to adjust the wire feed and other welding parameters. If the quality assessment system is not automatically informed about the change in the target values of the welding parameters, an incorrect assessment of the weld quality can result.

The object of the present invention is to create an above-mentioned method and a device for quality assessment of a machining process, through which the disadvantages described in relation to a deliberate change in the machining parameters during the machining process do not occur and a reproducible statement about the quality of the machining process and of the machined workpieces is made possible. Automatic quality assessment systems should also be used in the case of deliberate manual or automatic deviations in the processing parameters and be able to make reliable statements about the quality of the machining process or the machined workpiece.

The object according to the invention is achieved in terms of the method in that deviations in the processing parameters from the target values during the processing of the workpiece along the processing path are automatically taken into account when assessing the quality of the processing process, in that the quality parameter limit values are adapted to the deviations in the processing parameters. The method according to the invention therefore provides that the quality assessment system is informed of the actual values of the machining parameters during the machining process, as a result of which deliberately made changes to the target values of the machining parameters are automatically taken into account when assessing the quality of the machining process, by adjusting the quality parameter limit values accordingly to the deviations the processing parameters can be adjusted. As a result, the quality of the machined workpieces can be assessed more reliably and, for example, an unjustified reject of workpieces that are judged to be of inferior quality, or workpieces that are judged positively inadmissibly, although they do not meet the quality criteria, can be prevented. It is important that only deliberate or intentional deviations in the processing parameters are taken into account and no deviations caused by faults. Manually made changes to the target values of the machining parameters or automatically made changes to the target values of the machining parameters as a result of adaptive machining processes are considered to be intentional deviations. Target values of the processing parameters can be setting parameters, such as an average welding current to be set or an average wire feed, even if these processing parameters deviate from these set values during processing. The intentional deviations of the processing parameters from the target values can be transmitted to the place that carries out the quality assessment as standard or only if they occur. By taking into account the deviations of the processing parameters from the target values and an adjustment of the quality parameter limit values to the deviations in the processing parameters, the reliability of the quality assessment can be increased. The effects of changed processing parameters on the quality parameters can vary greatly depending on the type of processing. The relationship between deviations in the machining parameters and changes in the quality parameters for assessing the quality of the machining process or the machining result can be determined using test machining and stored in tables or functional relationships. Due to the automatic consideration during the quality assessment, it is possible that quality assessment systems can also be used with changed processing parameters due to the usual tolerances of the workpieces and deliver reliable results.

The deviations made in the processing parameters can be determined from the target values during the processing of the workpiece along the processing path by comparing the transmitted actual values of the processing parameters and transmitted target values of the processing parameters. The target values refer to those before the deviations made, the actual values to those after the changes made. With this so-called "online method", the deviations in the machining parameters are determined and transmitted in real time, so that the quality of the machining process along the machining path can be monitored at any time using the real data. The deviations in the processing parameters also include system-related deviations, which can occur, for example, when exchanging wear parts of the processing device. For example, the welding voltage will be reduced after replacing a contact tip of a welding torch. If these intended changes in the machining parameters and the associated changed quality parameter limit values are also taken into account when assessing the quality of the machining process, a more reliable statement about the quality of the machining process or of the workpiece machined during the machining process results.

Alternatively or additionally, the deviations made in the processing parameters from the target values and/or the transmitted actual values of the machining parameters and the transmitted target values of the machining parameters are also recorded during the machining of the workpiece along the machining path and are later used for automatic consideration when assessing the quality of the machining process along the machining path. With this so-called “offline method”, the deviations in the processing parameters and the associated limit values of the quality parameters are recorded and stored for later use, so that they can be used when monitoring the quality of the processing process.

According to a further feature of the invention, the quality parameter limit values adapted to the deviations in the processing parameters are determined from stored quality parameter limit values for specific processing parameters. If limit values for the resulting quality parameters, which can be used to assess the processing result, are stored for a wide variety of processing situations and various processing parameters, the quality parameter limit values can be determined from these stored values depending on the respective real processing parameters. Upper and lower quality parameter limit values can be specified as quality parameter limit values, or a quality parameter mean value with a specific maximum quality parameter fluctuation range can also be specified. The stored quality parameter limit values can be stored in the same memory or in the same database as the processing parameters or in other memories or databases.

The stored quality parameter limit values can be determined, for example, from test machining processes or machining trials, for example test welding processes or welding trials, with specific machining parameters and specific faults.

The quality parameter limit values adapted to the deviations in the processing parameters are preferably determined by interpolating the stored quality parameter limit values for specific Processing parameters determined. Such interpolation methods can be used to determine the respective quality parameter limit values for a wide variety of processing parameters quickly and without a great deal of computing effort.

When determining at least one quality parameter from at least one sensor signal for measuring the processing result, the deviation of at least one processing parameter is preferably taken into account. For example, when determining the seam width of a weld seam as a quality parameter of a welding process, a deviation in the feed speed of the welding wire can be taken into account, which has a significant influence on the seam width.

When assessing the quality of the machining process, additional environmental parameters such as the workpiece temperature, ambient temperature, humidity or the like can be taken into account. By including such environmental parameters, which can also depend on the machining path, the result of the quality assessment is improved even further.

The machining result along the machining path can be measured using non-destructive measuring methods, for example optical sensors, in particular laser scanners, cameras or the like, X-ray sensors and/or temperature sensors, and at least one sensor signal can be recorded. Recording the machining result using non-destructive measurement methods and preferably non-contact sensors has the advantage that the machining result can be measured particularly quickly and along the entire machining path, and the machined workpiece is not changed in the process. With certain influencing factors, it can be advantageous to measure the machining result along the machining path immediately after machining the workpiece. For example, the temperature curve in the material of the workpiece can provide information about the material structure of the machining result within and around the machining path immediately after the machining has been carried out. With certain quality parameters, it can also be advantageous to measure the processing result along the machining path some time after the workpiece has been machined, since the quality of the machining process can only be assessed after this time.

Alternatively or additionally, the processing result along the processing path can also be measured using destructive measuring methods, for example by making cuts through the workpiece at various points of the processing result along the processing path and in particular by producing images of the surface of the cuts, and at least one sensor signal can be recorded. For example, micrographs can be produced at specific intervals of the machining result along the machining path and specific quality parameters can be derived therefrom. Measurement methods of this type, which are naturally more complex, also provide essential information about the internal structure of the processing result along the processing path, which cannot be detected or can only be detected "poorly" with non-contact measuring methods. The micrographs recorded of the machining result along the machining path can in turn be analyzed using various methods, in particular using cameras and associated image processing methods. The use of certain chemicals can improve the recognition of the structure of the micrographs of the processing results. A macroscopic examination of micrographs after the machining process can also provide characteristic quality parameters. The micrographs are analyzed and determined and stored in the form of certain sensor signals and subsequently characterizing quality parameters of the machining result along the machining path. In addition to the production of microsections, tensile tests, bending tests, etc. on the workpieces are also conceivable.

According to a further feature of the invention, the processing result along the processing path is measured with the at least one sensor during the processing of the workpiece, the speed of measurement of the processing path preferably corresponding to the processing speed. In this embodiment variant, the quality of the machining process is assessed or the machining path of the workpiece immediately or a relatively short period of time after machining the workpiece. It is advantageous if the quality assessment system is moved synchronously with the processing system in relation to the workpiece. For example, a camera measuring the machining path can be mounted on the same robot arm that also carries the machining tool and can analyze the machining path after the workpiece has been machined. In this case, the machining result is measured along the machining path at the same speed as the machining of the workpiece. Of course, the quality assessment system and processing system can also stand still and the workpiece can move during processing, or both the quality assessment system and processing system and the workpiece can be moved against each other.

The machining result along the machining path can also be measured with at least one sensor after the machining of the workpiece has been completed, the speed of measuring the machining result along the machining path preferably being greater than the machining speed of the machining process. If the machining result is measured along the machining path independently of the machining of the workpiece, the measurement speed can also be selected to be significantly higher than the machining speed. For example, the optical scanning of the processing result along the processing path after processing a workpiece can take place much faster than processing the workpiece itself. In addition, several runs of measurements of the processing result along the processing path can also be carried out with different sensors and then from the different sensor signals the Quality parameters are determined. Furthermore, the workpieces from several processing stations can be assessed with a single measuring station.

If at least one quality parameter exceeds a specified quality parameter limit value or adjusted quality parameter limit value, a warning can be issued and/or or exceeding be saved. The warning can be given, for example, acoustically, optically or mechanically via a vibration mechanism. In this way, it is possible to point out that quality parameters have been exceeded. The warning can also be forwarded to higher-level authorities via appropriate communication channels.

The warning can be changed as a function of the degree to which at least one quality parameter is exceeded via a predefined quality parameter limit value or an adjusted quality parameter limit value. For example, the volume of an acoustic warning or the light intensity or flashing frequency of a visual warning can be adapted to the size of the quality deviation and the warning can be used to inform the staff of the size of the quality deviation.

In the case of a weld seam as the processing path, the processing parameters of the welding process welding current, welding voltage, conveying speed of a welding wire, angle of incidence of a welding torch to the workpiece, relative position of a welding torch to the workpiece and/or the welding speed are preferably taken into account. Such a welding process also includes a soldering process in which, in contrast to welding, there is little or no melting of the base material of the workpiece.

The object according to the invention is also achieved by an above-mentioned device for assessing the quality of a machining process, which is set up to carry out the above-mentioned method. Regarding the advantages that can be achieved in this way, reference is made to the above description of the method. The quality assessment device is characterized by a corresponding connection to the processing device, through which the changes made to the processing parameters are communicated to the quality monitoring device during processing, so that the limit values of the quality parameters can be automatically adapted to the deviations in the processing parameters.

Fig. 1

einen schematischen Bearbeitungsprozess, bei dem ein Werkstück mit bestimmten Bearbeitungsparametern entlang einer Bearbeitungsbahn bearbeitet wird;

Fig. 2A bis 2D

skizzieren schematisch ein Verfahren zur Qualitätsbeurteilung eines Bearbeitungsprozesses mit verschiedenen Sensoren zur Vermessung des Bearbeitungsergebnisses entlang der Bearbeitungsbahn;

Fig. 3

zeigt eine schematische Darstellung des erfindungsgemäßen Verfahrens zur Qualitätsbeurteilung eines Bearbeitungsprozesses an einem Werkstück; und

Fig. 4

ein Beispiel für eine bewusste Abweichung der Bearbeitungsparameter während eines Bearbeitungsprozesses und deren Berücksichtigung bei der Qualitätsbeurteilung des Bearbeitungsprozesses.

The present invention is illustrated by the accompanying drawings explained in more detail. Show in it:

1

a schematic machining process in which a workpiece is machined with specific machining parameters along a machining path;

Figures 2A to 2D

schematically outline a method for quality assessment of a machining process with various sensors for measuring the machining result along the machining path;

3

shows a schematic representation of the method according to the invention for assessing the quality of a machining process on a workpiece; and

4

an example of a deliberate deviation of the machining parameters during a machining process and their consideration in the quality assessment of the machining process.

1 shows a schematic machining process in which a workpiece W is machined with specific machining parameters P _i (x) along a machining path X to form a machining result R(x). The processing device 10 includes a processing robot 11, which carries the respective processing head 12, with which the workpiece W is processed, and along the processing path X to form the processing result R(x). To machine the workpiece W, certain target values of the machining parameters P _i,soll (x) are selected from a large number of possible machining parameters P _i (x), which are stored, for example, in a database or a memory 9, with which the workpiece W is machined. to achieve a desired processing result. Manual intervention on the machining device 10 or automatic mechanical intervention in adaptive machining processes (symbolized by the dot-dash line) can lead to changes in the setpoint values of the machining parameters P _i, setpoint (x) during the machining process and thus to desired or necessary deviations in the Processing parameters ΔP _i (x) come. With a subsequent quality monitoring of the machining result R(x) of the machining process by appropriate inspection of the machined workpiece W along the machining path X, such deviations in the machining parameters become apparent ΔP _i (x) of the setpoint values of the machining parameters P _i,soll (x) is usually not automatically taken into account in known methods, which can lead to incorrect assessments of the quality of the workpieces W. Due to the fact that conventional quality control systems fail in the event of deliberate deviations in the processing parameters ΔP _i (x), because the changed processing result R'(x) does not correspond to the expected processing result R(x), a complex manual check of the processing parameters with the deliberately changed processing parameters is usually required ΔP _i (x) machined workpieces W are made.

The processing device 10 can be a welding device for carrying out a joining process on a workpiece W, for example. In this case, a welding torch is attached to a welding robot, with which two or more workpieces W can be connected to one another or a layer can be applied to a workpiece W. In this case, the processing result R(x) is a weld seam between two or more workpieces W to be connected or a weld bead on the surface of a workpiece W. Furthermore, the processing device 10 can also be replaced by a device for treating the surface of a workpiece W with a plasma torch, a painting device and much more. Depending on the machining process, the machining result R(x) along the machining path X and also the assessment of the quality of the machining process and the respective machining result R(x) along the machining path X differ.

the Figures 2A to 2D show schematically a method for assessing the quality of a machining process with various sensors 2 for measuring the respective machining result R(x) of the machining process along the machining path X using a welding process as the machining process.

Figure 2A shows a quality assessment of the machining process, which takes place during or immediately after the machining of the workpiece W (so-called "online" quality assessment). Accordingly, the sensors 2 are for measuring the machining result R(x) of the machining process along the machining path X of the workpiece W is arranged on or behind the machining head 12, so that the machining result R(x) can be measured along the machining path X immediately after the machining process. The processing head 12 can be a welding torch 8, for example, via which a melting welding wire 7 is fed to the workpiece W for carrying out a joining process or build-up welding process. An arc LB burns between the end of the welding wire 7 and the workpiece W, which arc melts the welding wire 7 and the workpiece W. FIG. Possible sensors 2 for measuring the processing result R(x) along the processing path X of the workpiece W are, for example, optical sensors 3, cameras 4, X-ray sensors 5 or temperature sensors 6, which measure the processing result R(x) along the processing path X and corresponding sensor signals S _j (x) depending on the location along the machining path X. In the "online" quality assessment, the speed of measuring the processing result along the processing path X with the sensors 2 preferably corresponds to the speed of the processing process, ie the processing speed, for example the welding speed v _s (x) in a welding process.

As an alternative or in addition to the "online" quality assessment, according to Figure 2B an "offline" quality assessment can also take place, in which the workpiece W or the machining result R(x) along the machining path X is measured with appropriate sensors 2, for example optical sensors 3, cameras 4, or X-ray sensors 5 or the like, after the machining process has taken place and corresponding sensor signals S _j (x) are supplied. In the "offline" quality assessment, the speed of measurement of the machining result R(x) along the machining path X with the sensors 2 after the machining of the workpiece W has been completed can be greater than the machining speed. Nevertheless, the "offline" quality assessment, in contrast to the "online" quality assessment, represents an additional expenditure of time.

In Figure 2C a method of quality assessment of the machining process is outlined, in which the workpiece W for analysis of the machining result R(x) along the machining path X is destroyed in that micrographs of the workpiece W are produced at several points of the machining result R(x) along the machining path X in the region of the machining result R(x). These micrographs can be measured with appropriate sensors 2 and image processing methods and provide sensor signals S _j (x), which also provide information about the quality of the machining process on the workpiece W and the machining result R(x) at certain points along the machining path X. For example, such a micrograph can provide information about the penetration depth of the weld seam as a processing result R(x) during a welding process.

As in 2D illustrated, quality parameters Q _k (x) are determined from the various sensor signals S _j (x) of the machining result R(x), which characterize the quality of the machining result R(x) of the machining process for the respective machining task. Depending on the machining task, different and different numbers of quality parameters Q _k (x) can exist, which quantify the quality of the machining result R(x) along the machining path X. To assess the quality, the at least one quality parameter Q _k (x) is now compared with predefined quality parameter limit values, eg an upper quality parameter limit value Q _k,o (x) and a lower quality parameter limit value Q _k,u (x). If the quality parameter limit values Q _k,o (x), Q _k,u (x) are exceeded, the quality is assumed to be non-existent, which is marked with "NIO" (not OK). If all quality parameters Q _k (x) are within their quality parameter limit values Q _k,o (x), Q _k,u (x), the quality of the machining process is considered to be fulfilled and the workpiece W for "IO" (okay ) classified. If there are deliberate manual or automatically performed deviations in the machining parameters ΔP _i (x) during the machining process, the machining result R′(x) consequently changes. If this modified processing result R'(x) is now measured with the sensors 2 and quality parameters Q'k(x) are determined therefrom and compared with the original quality parameter limit values Q _k,o (x), Q _k,u (x). , this generally results in incorrect quality statements. Therefore, it is the concern of the present invention, the deliberately made deviations in the machining parameters ΔP _i (x) during the machining process when assessing the quality of the machining process and the changed machining result R'(x) automatically. This will preferably result in adjusted and changed quality parameter limit values Q' _k,o (x), Q' _k,u (x).

In 3 a schematic representation of the method according to the invention for assessing the quality of a machining process and the machining result R(x) along the machining path X on a workpiece W is shown. The device 1 for quality assessment of the machining process receives the various sensor signals S _j (x), which during the machining process are measured by sensors 2 mounted on the machining head 12 of the machining device 10 and the machining result R(x) along the machining path X ("online" - quality assessment). Alternatively or additionally, the device 1 is supplied with the sensor signals S _j (x) for quality assessment, which were recorded after the machining process by measuring the machining results R(x) along the machining paths X with corresponding sensors 2 . At least one quality parameter Q _k (x) is determined from the at least one sensor signal S _j (x) and the at least one quality parameter Q _k (x) for assessing the quality of the machining process and the machining result R(x) along the machining path X with specified quality parameters -Limit values Q _k,o (x), Q _k,u (x) compared. If the quality parameter limit values Q _k,o (x), Q _k,u (x) are exceeded, the quality is assumed to be unfulfilled and the workpiece is classified as "NOK" (not OK), which is indicated on a display 13, for example . If all quality parameters Q _k (x) are within their quality parameter limit values Q _k,o (x), Q _k,u (x), then the quality of the machining process and the machining result R(x) is considered to be fulfilled and the workpiece W classified for "IO" (okay) and displayed accordingly, for example, on the display 13. In addition, if a quality parameter limit value Q _k,o (x), Q _k,u (x) is exceeded, a warning can also be issued, for example an acoustic warning on a loudspeaker 14.

According to the invention, when assessing the quality of the machining process and the machining result R(x) along the machining path X, deviations of the machining parameters ΔP _i (x) from the setpoint values of the machining parameters P _i,soll (x) during the machining of the machining path X of the workpiece W automatically taken into account, which is illustrated by the connection of the machining device 10 to the device 1 for quality assessment of the machining process. This can be done, for example, by also defining adapted quality parameter limit values Q' _k,o (x), Q' _k,u (x) based on the changed situation, which are stored for the deviations in the processing parameters ΔP _i (x) or by corresponding calculation rules are defined. The automatic assessment of the quality of the machining process and the changed machining result R'(x) is thus automatically based on the adapted quality parameter limit values Q' _k,o (x), Q' _k,u (x), whereby the reliability of the quality monitoring is increased can be. Furthermore, this makes the quality assessment suitable for adaptive processing systems. As a result, workpieces W which, due to the tolerances that usually occur, are machined with modified machining parameters corresponding to the deviations in the machining parameters ΔP _i (x) and which deliver other machining results R'(x) than ideal workpieces W, can also be processed by the quality assessment system for "IO" (okay ) can be found without a time-consuming manual control having to be provided. The adjusted quality parameter limit values Q' _k,o (x), Q' _k,u (x) can be derived from stored quality parameter limit values Q _k,o,g (x), Q _k,u,g (x), which consist of Test machining processes are determined with certain machining parameters P _i (x), are determined, for example by interpolation of the stored quality parameter limit values Q _k,o,g (x), Q _k,u,g (x).

figure 4 shows an example of a deliberate deviation in the machining parameters ΔP _i (x) during a machining process and how it is taken into account in the quality assessment of the machining process using a welding process. In the left part of the figure, a workpiece W is shown in a sectional view above before processing and below after processing or after the welding process. This is about implementation an overlap weld seam on two overlapping workpieces W. Usually, the workpieces W lie on top of each other without a gap and the welding process is carried out with preset welding parameters. In quality monitoring, for example, the width B(x) and the height H(x) of the weld seam N is determined as a quality parameter along the processing path X and with specified limit values for the width B _o (x), B _u (x) and height H _o (x), H _u (x) of the weld N compared. If the conditions B _u (x) < B < _Bo (x) and H _u (x) < H < _Ho (x) are met, the quality of the machining process is assessed positively and the workpiece is classified as "OK".

In practice, tolerances usually occur, which can lead to a gap d between the workpieces W, for example, as in the right-hand part of FIG figure 4 shown. During the welding process, these changed conditions are reacted to, for example, manually or automatically (in the case of an adaptive welding process), for example by increasing the conveying speed v _d (x) of the welding wire and the welding current I(x) and reducing the welding speed v _s (x). The result is a weld seam N with a greater width B' and greater height H' than when machining the workpiece W without a gap d (left part of the figure 4 ). If the quality assessment is carried out without automatically taking into account the changed conditions and the consciously made changes to the processing parameters, the width B' and height H' of the weld seam N would be assessed as impermissible and the quality of the processing process would be assessed negatively and the workpiece would be rejected, for example ("NOK"). : out of order) or sent for manual review or post-processing.

In the method for quality assessment according to the invention, the deviations made in the processing parameters ΔP _i (x) are now taken into account by the quality assessment taking into account the deliberate changes or deviations in the processing parameters ΔP _i (x) (here, for example, the increases in the conveying speed v _d (x) and the welding current I(x) and the reduction in the welding speed v _s (x)) are announced and taken into account when assessing the quality. For example, due to the deviations in the processing parameters ΔP _i (x) adapted limit values of the quality parameters Q' _k,o (x), Q' _k,u (x) for the assessment of the quality of the machining process. In the example shown, the upper and lower limits for the width B' _o (x), B' _u (x) of the weld N and the upper and lower limits for the height H' _o (x), H' _u (x) of the weld seam N can be adjusted to the changed welding parameters. As a result, the changed processing result R'(x) or the changed weld seam N' is also correctly displayed in the right-hand part of the figure 4 judged positively in terms of quality since the conditions _B'u (x)<B'<_B'o (x) and _H'u (x)<H'<_H'o (x) are satisfied. Due to the automatic consideration of the deliberately made changes in the machining parameters ΔP _i (x) in the quality monitoring, the workpiece W can also be correctly classified as “OK” in this case and a manual check of the workpiece W can be omitted.

The adjusted limit values of the quality parameters Q' _k,o (x), Q' _k,u (x) in the event of deviations in the processing parameters ΔP _i (x) can, like the original limit values of the quality parameters Q _k,o (x), Q _{k, u} (x) for the normal machining parameters P _i (x) may be filed and stored in tables or according to specific regulations. Processing parameters P _i (x) lying between the stored values and limit values of the quality parameters Q _k,o (x), Q _k,u (x) can be determined by interpolation methods. The quality assessment system has access to this data, regardless of where it is available or stored. Instead of an upper and lower limit value for the quality parameters Q _k,o (x), Q _k,u (x), a quality parameter mean value Q _k,m (x) and a maximum quality parameter fluctuation range ΔQ _k around this mean value can be used to assess the Quality of the machining result R(x) can be used.

Claims (15)

A method for assessing the quality of a machining process in which a workpiece (W) is machined with certain machining parameters (P _i (x)) along a machining path (X), the machining result (R(x)) of the machining process along the machining path (X) with at least one sensor (2) is measured and at least one sensor signal (S _j (x)) is recorded and at least one quality parameter (Q _k (x)) is determined from at least one sensor signal (S _j (x)) and the at least one quality parameter ( Q _k (x)) to assess the quality of the machining result (R(x)) of the machining process along the machining path (X) with specified quality parameter limit values (Q _k,o (x), Q _k,u (x)). , characterized in that deviations made in the assessment of the quality of the machining process of the machining parameters (ΔP _i (x)) from the target values of the machining parameters (P _i, target (x)) during the machining of the workpiece cks (W) along the machining path (X) are automatically taken into account by adapting the quality parameter limit values (Q' _k,o (x), Q' _k,u (x)) to the deviations of the machining parameters (ΔP _i (x)) be adjusted. Method according to Claim 1, characterized in that the deviations made in the processing parameters (ΔP _i (x)) from the target values during the processing of the workpiece (W) along the processing path (X) by comparing the transmitted actual values of the processing parameters (P _i, actual). (x)) and transmitted nominal values of the machining parameters (P _i,nom (x)) are determined. Method according to Claim 1 or 2, characterized in that the deviations made in the processing parameters (ΔP _i (x)) from the setpoint values of the processing parameters (P _i, setpoint (x)) and/or the transmitted actual values of the processing parameters (P _i, actual (x)) and/or the transmitted nominal values of the machining parameters (P _i,nom (x)) recorded during the machining of the workpiece (W) along the machining path (X) and later for automatic consideration when assessing the quality of the machining process along the Machining path (X) are used. Method according to one of Claims 1 to 3, characterized in that the quality parameter limit values (Q' _k,o (x), Q' _k,u (x)) adapted to the deviations in the processing parameters (ΔP _i (x)) stored quality parameter limit values (Q _k,o,g (x), Q _k,u,g (x)) for specific processing parameters (P _i (x)) are determined. Method according to Claim 4, characterized in that the stored quality parameter limit values (Q _k,o,g (x), Q _k,u,g (x)) are determined from test machining processes with specific machining parameters (P _i (x)). Method according to Claim 4 or 5, characterized in that the quality parameter limit values (Q' _k,o (x), Q'k _,u (x)) adapted to the deviations in the processing parameters (ΔP _i (x)) are calculated by interpolating the stored quality parameter limit values (Q _k,o,g (x), Q _k,u,g (x)) for certain processing parameters (P _i (x)) are determined. Method according to one of Claims 1 to 6, characterized in that the deviation of at least one processing parameter (ΔP _i (x)) is taken into account when determining at least one quality parameter (Q _k (x)) from at least one sensor signal (S _j (x)). becomes. Method according to one of Claims 1 to 7, characterized in that additional environmental parameters (UP _i , UP _i (x)), such as workpiece temperature, ambient temperature, humidity or the like, are taken into account when assessing the quality of the machining process. Method according to one of Claims 1 to 8, characterized in that the processing result R(x) along the processing path (X) using non-destructive measuring methods, for example optical sensors (3), in particular laser scanners, cameras (4) or the like, X-ray sensors ( 5), and/or temperature sensors (6) are measured and at least one sensor signal (S _j (x)) is recorded. Method according to one of Claims 1 to 9, characterized in that the processing result R(x) along the processing path (X) using destructive measuring methods, for example by making cuts through the workpiece (W) at different points along the processing path (X) and Production of images of the surface of the cuts measured and at least one sensor signal (S _j (x)) is recorded. Method according to one of Claims 1 to 10, characterized in that the machining result R(x) along the machining path (X) is measured with the at least one sensor (2) during the machining of the workpiece (W), the speed of the measurement of the Processing path (X) preferably corresponds to the processing speed. Method according to one of Claims 1 to 10, characterized in that the machining result R(x) along the machining path (X) is measured with at least one sensor (2) after the machining of the workpiece (W) has been completed, the speed of the measurement of the Processing path (X) is preferably greater than the processing speed. Method according to one of Claims 1 to 12, characterized in that when at least one quality parameter (Q _k (x)) is exceeded above a predetermined quality parameter limit value (Q _k,o (x), Q _k,u (x)) or an adapted Quality parameter limit value (Q' _k,o (x), Q' _k,u (x)) a warning is issued and/or the exceeding is stored. Method according to one of Claims 1 to 13, characterized in that in the case of a weld seam as the processing path (X), the processing parameters (P _i (x)) of the welding process welding current (I(x)), welding voltage (U(x)), conveying speed (v _d (x)) of a welding wire (7), setting angle (α(x)) of a welding torch (8) to the workpiece (W), relative position of a welding torch (8) to the workpiece (W) and/or the welding speed (v _s (x)) must be taken into account. Device (1) for assessing the quality of a machining process of a workpiece (W) with specific machining parameters (P _i (x)) along a processing path (X) which is designed to carry out the method according to one of Claims 1 to 14.

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